Drugs Affecting the Respiratory System

1. Drugs Affecting the Respiratory System

2. OVERVIEW • Drugs can be delivered to the lungs by inhalation, oral, or parenteral routes. Inhalation is often preferred because the drug is delivered directly to the target tissue--the airways--and is effective in doses that do not cause significant systemic side effects.

3. DRUGS USED TO TREAT ASTHMA • Asthma is a chronic disease that affects 4 to 5% of the U.S. population, or approximately 10 million patients. • The disease is characterized by episodes of acute bronchoconstriction causing shortness of breath, cough, chest tightness, wheezing and rapid respirations.

4. Role of inflammation in asthma • Airflow obstruction in asthma is due to bronchoconstriction resulting from contraction of bronchial smooth muscle, inflammation of the bronchial wall, and increased mucous secretion. • may be related to recent exposure to allergens, inhaled irritants leading to bronchial hyperactivity and inflammation of the airway mucosa.

5. Adrenergic agonists • Inhaled adrenergic agonists with beta-2 activity are the drugs of choice for mild asthma, that is, in patients showing only occasional, intermittent symptoms beta-2 Agonists are potent bronchodilators that relax airway smooth muscle directly.

6. Short acting drugs • Most clinically useful beta-agonists have a rapid (15 to 30 minutes) onset of action and provide relief for 4 to 6 hours. • They are used for symptomatic treatment of bronchospasm and as "rescue agents" to combat acute bronchoconstriction.

7. Long acting drugs • Salmeterol xinatoate is a chemical analog of albuterol, but differs by having a long lipophilic side chain that increases the affinity of the drug for the beta-adrenoceptor.

8. Corticosteroids • Inhaled glucocorticoids are the drugs of first choice in patients with moderate to severe asthma who require inhalation of beta-adrenergic agonists more than once daily

9. Actions on lung • Steroids have no direct effect on the airway smooth muscle. Instead, inhaled glucocorticoids decrease the number and activity of cells involved in airway inflammation-macrophages, eosinophils, and T-lymphocytes.

10. Pharmacokinetics • Inhaled drugs: has markedly reduced the need for systemic corticosteroid treatment. However, a few precautions are required for successful inhalation therapy. A large fraction (typically 80 to 90%) of inhaled glucocorticoids is deposited in the mouth and pharynx, or is swallowed

11. Pharmacokinetics • Systemic steroids: Patients with severe exacerbation of asthma (status asthmaticus) may require intravenous admin- istration of methylprednisolone or oral prednisone

12. DRUGS USED TO TREAT ALLERGIC RHINITIS • Rhinitis is an inflammation of the mucous membranes of the nose, and is characterized by sneezing, nasal itching, watery rhinorrhea and congestion.

13. Antihistamines (H1 receptor blockers) • Antihistamines are the most frequently used agents in the treatment of sneezing and watery rhinorrhea associated with allergic rhinitis. H1-Histamine receptor blockers, such as diphenhydramine, chlorpheniramine, Ioratadine, terfenadine and astemizole are useful in treating the symptoms of allergic rhinitis caused by histamine release.

14. alpha-Adrenergic agonists • alpha-Adrenergic agonists ("nasal decongestants") such as phenylephrine, constrict dilated arterioles in the nasal mucosa and reduce airway resistance.

15. Corticosteroids • Corticosteroids are effective when administered as nasal sprays. Topical steroids may be more effective than systemic antihistamines in relieving the nasal symptoms of both allergic and nonallergic rhinitis.